Add Switchboard to Categories

This MR adds sections for Switchboard to categories.yml and stages.yml. Switchboard has its own development resources and roadmap, so we'd like it to be distinct from the GitLab Dedicated.

A Switchboard direction page is also being added - see !124456 (merged)

Approvals

Merge requests with changes to stages and groups and significant changes to categories need to be created, approved, and/or merged by each of the below:

• Chief Product Officer @david
• The Product Director relevant to the affected Section(s)
• The Engineering Director relevant to the affected Section(s)
• Director of Product Design @vkarnes

The following people need to be on the merge request so they stay informed:

• Vice President of Development @clefelhocz1
• Vice President of Quality @meks
• Vice President of User Experience @clenneville
• The Product Marketing Manager relevant to the stage group(s)
• Director of Technical Writing @susantacker

After Approvals and Merge

• Create an issue in the triage-ops project to update GitLab Bot automation:
  • for Category change
  • for Stage or Group change
  • If label migration is required, please follow the self-serve instructions to get started on a one-off label migration MR.
• Mention the product group Technical Writer to update the documentation metadata
• Share MR in #product, #development, and relevant #s_, #g_, and #f_ slack channels